I don't think that the exception in my second message caused by that code.
Basically I've removed it all together and still getting the same exception.
In your experience what could cause the "Unexpected exception while processing element 'inherits'" with references to problems with class loader and XML parsing failures (full stack trace posted above)?
Maybe you know about any standard omissions that people do while migrating from myGWT 0.5.x to GXT that could cause this type of issues?